Sql Distinct | Distinct command in sql - sql tutorial - learn sql

DISTINCT command in SQL collects the unique or distinct records from a field of a table.
The SQL DISTINCT keyword is used in conjunction with the SELECT statement to eliminate all the duplicate records and fetching only unique records.
There may be a situation in which you have multiple duplicate records in a table.
When fetching such records, it makes more sense to fetch only those unique records instead of fetching duplicate records.
Any value that has a duplicate will only show up once.

SQL Distinct

Syntax

SELECT DISTINCT "column_name"
FROM "table_name";

"table_name" is the name of the table where data is stored, and "column_name" is the name of the column containing the data to be retrieved.

Examples

The examples will use the following table:

Table Store_Information

Store_Name	Sales	Txn_Date
Los Angeles	1500	Jan-05-1999
San Diego	250	Jan-07-1999
Los Angeles	300	Jan-08-1999
Boston	700	Jan-08-1999

Read Also

Insert into select.

Example 1: Use DISTINCT on one column

To select all distinct stores in Table Store_Information,

SELECT DISTINCT Store_Name FROM Store_Information;

Result:

Store_Name
Los Angeles
San Diego
Boston

Example 2: Use DISTINCT on multiple columns

We can apply DISTINCT to multiple columns. If we want to get a list showing all unique combinations of stores and transaction dates, we would type in the following,

SELECT DISTINCT Store_Name, Txn_Date FROM Store_Information

Result:

Store_Name	Txn_Date
Los Angeles	Jan-05-1999
San Diego	Jan-07-1999
Los Angeles	Jan-08-1999
Boston	Jan-08-1999

Exercises

For these exercises, assume we have a table called Users with the following data

Table Users

First_Name	Last_Name	Birth_Date	Gender	Join_Date
Sophie	Lee	Jan-05-1960	F	Apr-05-2015
Richard	Brown	Jan-07-1975	M	Apr-05-2015
Casey	Healy	Sep-20-1969	M	Apr-09-2015
Jamal	Santo	Oct-08-1983	M	Apr-09-2015
Jill	Wilkes	Nov-20-1979	F	Apr-15-2015

Interview questions in distinct command in SQL:

Example 1

1. Which of the following SQL statement is valid ?

a) SELECT DISTINCT * FROM Users; 
b) SELECT DISTINCT First_Name FROM Users; 
c) SELECT DISTINCT First_Name Last_Name FROM Users

Answer:

SELECT DISTINCT First_Name FROM Users;

Read Also

Inline view in sql.

Example 2

2. What's the result of the following query ?

SELECT DISTINCT Join_Date From Users;

Answer

Join Date
Apr-05-2015
Apr-09-2015
Apr-15-2015

Example 3

3. What's the result of the following query ?

SELECT DISTINCT Gender, Join_Date From Users;

Answer

Gender	Join_Date
F	Apr-05-2015
M	Apr-05-2015
M	Apr-09-2015
F	Apr-15-2015

SQL DISTINCT Sample Application

SQL Distinct Example

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